Various microscopes are used for observing samples such as cells. Patent Document 1 discloses a microscope which optically scans a sample. An observer may use the microscope to observe the sample.
FIG. 17 is a schematic view of a scanning optical microscope (hereinafter, referred to as a microscope 900) of Patent Document 1. The microscope 900 is described with reference to FIG. 17.
The microscope 900 includes a laser source 901, a beam splitter 902, a lens 903, an acousto-optic deflector (hereinafter, referred to as an AOD 904) and a signal source 905. The laser source 901 emits a laser beam to the beam splitter 902. The beam splitter 902 reflects the laser beam to the lens 903. The laser beam is then incident on the AOD 904 through the lens 903.
The signal source 905 outputs a driving signal to the AOD 904. The AOD 904 changes a grating constant (grating width) of an ultrasonic diffraction grating, caused in a crystalline medium in response to the driving signal. Consequently, the AOD 904 may control deflection of the laser beam.
The microscope 900 further includes mirrors 906, 907, a lens 908, a resonant galvanometer 909, a resonant vibration mirror 910 and a signal source 911. The AOD 904 performs a one-dimensional scanning operation at high speed. The laser beam is then reflected to the mirror 907 by the mirror 906. The laser beam is reflected to the lens 908 by the mirror 907. The laser beam passes through the lens 908, and reaches the resonant vibration mirror 910 mounted on the galvanometer 909.
The signal source 911 outputs a driving signal to the galvanometer 909. The galvanometer 909 resonantly vibrates the resonant vibration mirror 910 in response to the driving signal. Consequently, the laser beam is reflected by the resonant vibration mirror 910 performing a sinusoidal deflection operation.
The galvanometer 909 and the resonant vibration mirror 910 perform a scanning operation in a direction orthogonal to a direction of the scanning operation performed by the AOD 904. The galvanometer 909 and the resonant vibration mirror 910 perform a two-dimensional scanning operation in cooperation with the AOD 904.
The microscope 900 further includes spherical relay mirrors 912, 913, a galvanometer 914, a galvanomirror 915 and a signal source 916. The laser beam is reflected from the resonant vibration mirror 910 to the spherical relay mirror 912. The spherical relay mirror 912 reflects the laser beam to the spherical relay mirror 913. The spherical relay mirror 913 reflects the laser beam to the galvanomirror 915 mounted on the galvanometer 914.
The signal source 916 outputs a driving signal to the galvanometer 914. The galvanometer 914 drives the galvanomirror 915 in response to the driving signal. The galvanometer 914 and the galvanomirror 915 perform a scanning operation in a direction parallel to a direction of the scanning operation performed by the AOD 904. In short, the galvanometer 914 and the galvanomirror 915 perform the scanning operation in a direction orthogonal to the direction of the scanning operation of the galvanometer 909 and the resonant vibration mirror 910.
The microscope 900 further includes a beam splitter 917, a relay lens 918 and an object lens 919. The laser beam reflected by the galvanomirror 915 is incident on the object lens 919 through the beam splitter 917 and the relay lens 918. The object lens 919 condenses light on a sample SMP.
The microscope 900 includes an object lens 920, a mirror 921, a relay lens 922, a mirror 923, a wavelength plate 924, a polarization plate 925, a pentagonal prism 926 and a relay lens 927. The sample SMP is situated between the object lenses 919, 920. The object lens 920 has optical characteristics analogous to the object lens 919. The object lens 920, the mirrors 921, 923, the relay lenses 922, 927, the wavelength plate 924, the polarization plate 925 and the pentagonal prism 926 are used to observe a transmission image represented by transmission light which passes through the sample SMP. The transmission light propagates along an optical path defined by the object lens 920, the mirror 921, the relay lens 922, the mirror 923, the wavelength plate 924, the polarization plate 925, the pentagonal prism 926 and the relay lens 927. The transmission light passing through the relay lens 927 is incident on the beam splitter 917. The transmission light is reflected by the beam splitter 917. Consequently, the transmission light propagates along the optical path defined by the beam splitter 917, the galvanomirror 915, the spherical relay mirrors 913, 912, the resonant vibration mirror 910, the lens 908, the mirrors 907, 906, the AOD 904 and the lens 903 to be incident on the beam splitter 902.
The wavelength plate 924 and the polarization plate 925 use rotation of a polarization face of light to allow detection of only the transmission light. There is little optical loss resulting from the wavelength plate 924 and the polarization plate 925.
The pentagonal prism 926 reverses the optical path of the transmission light in a one-dimensional direction. Consequently, the optical path of the transmission light is combined with the optical path of the laser beam emitted from the laser source 901.
The microscope 900 further includes a lens 928, a confocal opening member 929, a polarization plate 930, a filter 931 and a photo receiver 932. The beam splitter 902 allows passage of the transmission light. The transmission light sequentially passes through the lens 928, the confocal opening member 929, the polarization plate 930 and the filter 931 to enter into the photo receiver 932.
The lens 928 condenses light toward the confocal opening member 929. The confocal opening member 929 has an opening portion 933 at a focal position defined by the lens 928. Accordingly, the confocal opening member 929 and the sample SMP are conjugate with each other optically. The confocal opening member 929 blocks stray light components around the focal point. Consequently, there are improved resolution and contrast of an obtained image.
The microscope 900 may use light reflected from the sample SMP to form an image. The light reflected from the sample SMP propagates along the optical path defined by the object lens 919, the beam splitter 917, the galvanomirror 915, the spherical relay mirrors 913, 912, the resonant vibration mirror 910, the lens 908, the mirrors 907, 906, the AOD 904, the lens 903, the beam splitter 902, the confocal opening member 929, the polarization plate 930 and the filter 931 to be incident on the photo receiver 932.
As described above, since the confocal opening member 929 blocks the stray light components around the focal point, a lot of stray light components are removed from the Eight (transmission light and reflection light) which the photo receiver 932 receives. Accordingly, the photo receiver 932 may generate an image signal for representing a sample under little noise.
An observer may adjust polarization directions of the polarization plates 925, 930 to selectively observe an image (hereinafter, referred to as a transmission image) represented by transmission light and an image (hereinafter, referred to as a reflection image) represented by reflection light.
The microscope 900 further includes a signal processing device 934 and a display device 935. The image signal is transmitted from the photo receiver 932 to the signal processing device 934. The signal processing device 934 processes the image signal to adapt the image signal to an input format of the display device 935. The image signal is then output from the signal processing device 934 to the display device 935. The display device 935 displays the transmission image or the reflection image in response to the image signal.
An observer using the microscope 900 to observe the sample SMP may not obtain both of the transmission image and the reflection image without adjustment to the polarization directions of the polarization plates 925, 930. Accordingly, it necessarily takes a long time for the observer to obtain both of information contained in the transmission image and information contained in the reflection image. In addition, there is a time lag between acquisitions of the transmission image and the reflection image. Accordingly, the microscope 900 is not suitable for observation of a sample changing over time.
Patent Document 2 discloses a microscope (confocal microscope) different from the microscope 900. The microscope of Patent Document 2 is used very suitably to detect defects of a photomask.
The microscope of Patent Document 2 emits a laser beam to optically scan the photomask. The laser beam (transmission light) passing through the photomask propagates along the optical path which is common with the reflection light obtained by reflection of the laser beam on the photomask. The microscope may perform correlation processes between the transmission image and the reflection image to detect defects of the photomask very accurately.
Accuracy in detection of the microscope of Patent Document 2 depends on optical characteristics of a sample. For example, if a sample causes birefringence, a part of the reflection image may be contained in the transmission image. Alternatively, a part of the transmission image may be contained in the reflection image.